1. Field of Invention
The present invention relates to an embedded information/alteration detection apparatus as well as an embedded information/alteration detection method, and a computer-readable record medium storing an embedded information/alteration detection program therein, which embeds information by chiefly utilizing redundancy existent concerning the description method of a data structure, in order to detect the alteration or the legitimacy of the data. More particularly, the invention relates to data hiding technology which embeds information into data describing a three-dimensional shape, such as three-dimensional design data generated in such, as three-dimensional graphics and CAD. The invention also relates to a technology which detects the alteration or legitimacy of the data of a three-dimensional shape composed as the combination of primitive geometric shapes, such as a polyhedron and a body of revolution.
2. Description of Related Art
Heretofore, digital watermark technology and data hiding technology as described below have been known in the related art.
JP-A-10-334272 for example, contains a technique wherein information is embedded by changing the geometry parameters of a three-dimensional shape model.
Specifically, the related-art technique adopts a method wherein various information items are embedded into the three-dimensional shape model in a visible or invisible state by changing the geometry parameters of the three-dimensional shape model, namely, a description to define a geometric shape.
The three-dimensional shape model being a subject for embedding is usually composed of its primitives (constituents) that are polyhedrons, straight lines, sets of points, or curved surfaces. Each of the primitives is defined by geometry parameters. Accordingly, the three-dimensional shape model has its whole geometric shape defined by the set of a large number of geometry parameters.
As stated in the related-art technique, therefore, the information is embedded by changing the geometry parameters of a plurality of primitives which constitute the three-dimensional shape model.
It is also described in the related-art technique that the information is embedded by dividing the geometry parameters into numerical parameters and phases and then changing the respective divisions, and that the embedded information is conversely extracted by detecting the changed geometry parameters.
Further, JP-A-2000-82156 contains a technique wherein the data of a three-dimensional shape model is submitted to a wavelet transform, and information is embedded into the result of the transform.
Specifically, according to this related-art example, three-dimensional shape transformation means performs wavelets transformation on the data of an original model V0 and digital watermark embedding means embeds watermark data into a WT factor vector generated by the wavelet transformation. Inverse transformation means of a three-dimensional shape creates the data of a three-dimensional shape model (distribution model V′0) in which the watermark data is embedded, on the basis of the WT factor vector.
Thus, according to the related-art technique, in a case where the data of digital information, including copyright information,etc., is embedded into three-dimensional shape data, the error control can be performed in consideration of the visual change of the three-dimensional shape model in which the digital information data is embedded. A robust digital information data embedding method is described even when the shape model is deleted or deformed.